libvirt: When building image with boot_config != null, build image in…

… two stages to share the first build

nix/libvirtd-image.nix

@@ -1,4 +1,11 @@
-rec {
+let
+ makeconfig = { system, config }:
+ (import <nixpkgs/nixos/lib/eval-config.nix> {
+ inherit system;
+ modules = [ config ];
+ }).config;
+
+in rec {
  base_image_config = {
  fileSystems."/".device = "/dev/disk/by-label/nixos";
 
@@ -15,10 +22,7 @@ rec {
  config ? base_image_config
  }:
  let
- cfg = (import <nixpkgs/nixos/lib/eval-config.nix> {
- inherit system;
- modules = [ config ];
- }).config;
+ cfg = makeconfig { inherit system config; };
 
  in pkgs.vmTools.runInLinuxVM (
  # TODO: Use <nixpkgs/nixos/lib/make-disk-image.nix> when
@@ -129,4 +133,82 @@ rec {
  );
 
 
+ deploy_in_nixos_image = {
+ system ? builtins.currentSystem,
+ pkgs ? import <nixpkgs> {},
+ base_image,
+ config
+ }:
+ let
+ cfg = makeconfig { inherit system config; };
+
+ in pkgs.vmTools.runInLinuxVM (
+ pkgs.runCommand "libvirtd-deploy-in-nixos-image"
+ { memSize = 768;
+ preVM =
+ ''
+ mkdir $out
+ diskImage=$out/image
+ ${pkgs.vmTools.qemu}/bin/qemu-img create -f qcow2 -b ${base_image}/disk.qcow2 $diskImage
+ mv closure xchg/
+ '';
+ postVM =
+ ''
+ mv $diskImage $out/disk.qcow2
+ '';
+ buildInputs = [ pkgs.utillinux pkgs.perl ];
+ exportReferencesGraph =
+ [ "closure" cfg.system.build.toplevel ];
+ }
+ ''
+ . /sys/class/block/vda1/uevent
+ mknod /dev/vda1 b $MAJOR $MINOR
+ mkdir /mnt
+ mount /dev/vda1 /mnt
+
+ # The initrd expects these directories to exist.
+ mount --bind /proc /mnt/proc
+ mount --bind /dev /mnt/dev
+ mount --bind /sys /mnt/sys
+
+ # Avoid "groups does not exist" warnings
+ mkdir -p /etc/nix
+ echo 'build-users-group = ' > /etc/nix/nix.conf
+ mkdir -p /mnt/etc/nix
+ echo 'build-users-group = ' > /mnt/etc/nix/nix.conf
+
+ sourceStore='${pkgs.nix}/bin/nix-store'
+ targetStore='chroot /mnt ${cfg.nix.package.out}/bin/nix-store'
+
+ echo "filling Nix store..."
+ set -f
+
+ # Copy missing paths in the closure to the target nix store.
+ storePaths=$(perl ${pkgs.pathsFromGraph} /tmp/xchg/closure)
+ missing=$(NIX_DB_DIR=/mnt/nix/var/nix/db $sourceStore --check-validity --print-invalid $storePaths)
+ for path in $missing; do
+ ${pkgs.rsync}/bin/rsync -a $path /mnt/nix/store/
+ done
+
+ # Register the paths in the Nix database.
+ $targetStore --register-validity < /tmp/xchg/closure
+
+ # TODO: Replace with the following
+ # when https://github.com/NixOS/nix/issues/1134 is fixed
+ #printRegistration=1 perl ${pkgs.pathsFromGraph} /tmp/xchg/closure | $sourceStore --load-db
+ #$sourceStore --export $missing | $targetStore --import
+
+
+ # Create the system profile to allow nixos-rebuild to work.
+ chroot /mnt ${cfg.nix.package.out}/bin/nix-env \
+ -p /nix/var/nix/profiles/system --set ${cfg.system.build.toplevel}
+
+ # Generate the GRUB menu.
+ ln -s vda /dev/sda
+ chroot /mnt ${cfg.system.build.toplevel}/bin/switch-to-configuration boot
+
+ umount /mnt/proc /mnt/dev /mnt/sys
+ umount /mnt
+ ''
+ );
 }

nix/libvirtd.nix

@@ -13,13 +13,13 @@ let
  services.openssh.extraConfig = "UseDNS no";
  };
 
- ssh_image = if config.deployment.libvirtd.boot_config == null then
- let base_image = libvirt_image_helpers.create_nixos_image {
- size = sz;
- config = base_config;
- };
+ base_image = libvirt_image_helpers.create_nixos_image {
+ size = sz;
+ config = base_config;
+ };
 
- in libvirt_image_helpers.edit_image {
+ ssh_image = if config.deployment.libvirtd.boot_config == null then
+ libvirt_image_helpers.edit_image {
  inherit pkgs base_image;
  cmd = ''
  mkdir -p /mnt/etc/ssh/authorized_keys.d
@@ -28,9 +28,8 @@ let
  }
 
  else
- libvirt_image_helpers.create_nixos_image {
- inherit pkgs;
- size = sz;
+ libvirt_image_helpers.deploy_in_nixos_image {
+ inherit pkgs base_image;
  config.imports = [
  base_config
  { users.users.root.openssh.authorizedKeys.keys = [ ssh_pubkey ]; }